ata: expose ncq_enable_prio sysfs attribute only on NCQ capable hosts

There is no point in exposing ncq_enable_prio sysfs attribute for
devices on PATA and non-NCQ capable SATA hosts so:

* remove dev_attr_ncq_prio_enable from ata_common_sdev_attrs[]

* add ata_ncq_sdev_attrs[]

* update ATA_NCQ_SHT() macro to use ata_ncq_sdev_attrs[]

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index ebc3de7..005c6f2 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -463,11 +463,17 @@ EXPORT_SYMBOL_GPL(dev_attr_sw_activity);
 
 struct device_attribute *ata_common_sdev_attrs[] = {
 	&dev_attr_unload_heads,
-	&dev_attr_ncq_prio_enable,
 	NULL
 };
 EXPORT_SYMBOL_GPL(ata_common_sdev_attrs);
 
+struct device_attribute *ata_ncq_sdev_attrs[] = {
+	&dev_attr_unload_heads,
+	&dev_attr_ncq_prio_enable,
+	NULL
+};
+EXPORT_SYMBOL_GPL(ata_ncq_sdev_attrs);
+
 /**
  *	ata_std_bios_param - generic bios head/sector/cylinder calculator used by sd.
  *	@sdev: SCSI device for which BIOS geometry is to be determined